The pair of compounds that can exist together is

1. FeCl₃, SnCl₂             

2. HgCl₂, SnCl₂

3. FeCl₂, SnCl₂             

4. FeCl₃, KI

A mixture of potassium chlorate, oxalic acid and sulphuric acid is heated. During the

reaction which element undergoes a maximum change in the oxidation number?

1. S

2. H

3. Cl

4. C

The oxidation states of P in H₄P₂O₅, H₄P₂O₆, H₄P₂O₇, are respectively -

The number of moles of MnO^-₄ required to oxidise one mole of ferrous oxalate completely in an acidic medium is-

1. 0.6 mole

2. 0.4 mole

3. 7.5 moles

4. 0.2 mole

Which one of the following orders correctly represents the increasing acid strengths of the given acids?

(1) HOCl <HOClO <HOClO₂ < HOClO₃

(2) HOClO <HOCl <HOClO₃ <HOClO₂

(3) HOClO₂ <HOClO₃ <HOClO <HOCl

(4) HOClO₃> HOClO₂ <HOClO <HOCl

The correct order of N-compounds in its decreasing order of oxidation states is :

1. ${\mathrm{HNO}}_3,$ $\mathrm{NO},$ ${\mathrm{N}}_2,$ ${\mathrm{NH}}_4\mathrm{Cl}$

2. ${\mathrm{HNO}}_3, \mathrm{NO}, {\mathrm{NH}}_4\mathrm{Cl}, {\mathrm{N}}_2$

3. ${\mathrm{HNO}}_3, {\mathrm{NH}}_4\mathrm{Cl}, \mathrm{NO}, {\mathrm{N}}_2$

4. ${\mathrm{NH}}_4\mathrm{Cl}, {\mathrm{N}}_2, \mathrm{NO}, {\mathrm{HNO}}_3$

For the redox reaction,
 a${\mathrm{MnO}}_4^{-}+{\mathrm{bC}}_2{\mathrm{O}}_4^{2-}+{\mathrm{cH}}^{+}\to {\mathrm{dMn}}^{2+}+{\mathrm{eCO}}_2+{\mathrm{fH}}_2\mathrm{O}$
the correct stoichiometric coefficients of the reactants a, b, and c respectively for the balanced equation are: 

1. 16, 5, 2
2. 2, 5, 16
3. 2, 16, 5
4. 5, 16, 2

The change in oxidation number of chlorine when Cl₂ gas reacts with hot and concentrated sodium hydroxide solution is:

1. Zero to +1 and Zero to –5

2. Zero to –1 and Zero to +5

3. Zero to –1 and Zero to +3

4. Zero to +1 and Zero to –3

The highest oxidation number of nitrogen among the following compounds is:

Oxidation numbers of P in ${\mathrm{PO}}_4^{3-}$, of S in ${\mathrm{SO}}_4^{2-}$ and that of Cr in ${\mathrm{Cr}}_2{\mathrm{O}}_7^{2-}$are respectively:
1. +5, +6 and +6
2. +3, +6 and +5
3. +5, +3 and +6
4. -3, +6 and +6